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Old President Grant same cobra 138XLR and Trc449 odd problem not sure where to start.

Low_Boy

Low_Boy

Sr. Member
Jan 21, 2010
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Rochester N.Y.
There is no Sam's on this radio but there is one for the TRC 449 and 138XLR and a TRC 449 service manual.

My notes are sketchy. This has been a work in progress for several years. I had removed the extra cannels and relocked the clarifier years ago. I remembered and the notes say Sometimes works on LSB. Sometimes there is frequency on AM and USB.

I pulled tis out of the pile remembering last time I looked at it it had no TX and RX. So after doing something to this radio. Which seemed like someone screwed the TVI trap all the way in it is now keying up on all channels 22.6750 MHz it is also keying on SSB around the same freq. So yes there is a carrier on SSB. It receives perfectly. All PLL settings adjust to where they belong VR 9 does not work. Not quite sure what I am looking for. I believe I am missing a frequency or a voltage. but not sure why there is a carrier on SSB and all channels no matter where the thing is set show the same frequency? Also I have tried to post this 3 times and the page keeps going away or locking.
 
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Are you sure that the one in CB-126 is not yours? I am looking at it AND the TRC 449 AND the 138XLR and they all look identical just scanning through.....
 
Low_Boy said:
There is no Sam's on this radio but there is one for the TRC 449 and 138XLR and a TRC 449 service manual.

My notes are sketchy. This has been a work in progress for several years. I had removed the extra cannels and relocked the clarifier years ago. I remembered and the notes say Sometimes works on LSB. Sometimes there is frequency on AM and USB.

I pulled tis out of the pile remembering last time I looked at it it had no TX and RX. So after doing something to this radio. Which seemed like someone screwed the TVI trap all the way in it is now keying up on all channels 22.6750 MHz it is also keying on SSB around the same freq. So yes there is a carrier on SSB. It receives perfectly. All PLL settings adjust to where they belong VR 9 does not work. Not quite sure what I am looking for. I believe I am missing a frequency or a voltage. but not sure why there is a carrier on SSB and all channels no matter where the thing is set show the same frequency? Also I have tried to post this 3 times and the page keeps going away or locking.
Click to expand...

http://www.kenselectronics.com/lists/sams.htm

shows CB-127 (Grant with 858 chassis) as available for $12.95

You can also get a hard copy/download of the CB-127 that covers the Grant from SAMS for $22
https://www.samswebsite.com/en/photofact/details/index/id/119601

if you live near a large city, there is a good chance that the main library has a set of the CB photofacts and will have CB-127. You can go there and "check it out"...

I am sure there are members here that have a copy of CB-127 and could probably help you out.
 
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Dr_DX said:
http://www.kenselectronics.com/lists/sams.htm

shows CB-127 (Grant with 858 chassis) as available for $12.95

You can also get a hard copy/download of the CB-127 that covers the Grant from SAMS for $22
https://www.samswebsite.com/en/photofact/details/index/id/119601

if you live near a large city, there is a good chance that the main library has a set of the CB photofacts and will have CB-127. You can go there and "check it out"...

I am sure there are members here that have a copy of CB-127 and could probably help you out.
Click to expand...
Dr_DX said:
http://www.kenselectronics.com/lists/sams.htm
Click to expand...

Kens Electronics has been a good source of hard to find stuff for years.
He has helped me out in the past.

73
Jeff
 
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call austin texas public library,they got full set of sams and will gladly send you any sams you want via pdf . very nice people there also
 
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AudioShockwav said:
Kens Electronics has been a good source of hard to find stuff for years.
He has helped me out in the past.

73
Jeff
Click to expand...
Ken is great! I live in Michigan and it has been prob. 10+ years since I have been to his shop. His mom was still alive and riding her 3 wheeled bike every day last time I was their and he had a red head working in the shop! I bought 2 transformers for a tube amp I was building at the time. He is about 2 hours from me. I have been meaning to go see him for about 3 years now. Hope he is doing well!
 
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I messed with this again today all PLL Voltages were correct. VCO Block had all correct voltages. But I was wrong CT6, CT5, CT4, CT#3 and CT2 do not adjust.
 
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Makes me wonder if this radio was built with the white ceramic-body trimmer caps for CT4-6. You didn't mention CT3, so I'll guess that one behaves properly when you twist it.

That particular style trimmer cap can become seized. The metal-coated ceramic doughnut is what actually turns with the adjusting screw. The metalized layer on half of that doughnut is soldered to that screw.

If the doughnut gets stuck to the trimmer's body, the natural reaction is to twist harder.

Until a tiny "CRACK!" sound is heard and the screw suddenly turns freely.

Very freely. Because the solder connection from that screw to the metal coating on the doughnut is now broken. The trimmer will now be functionally stuck at minimum, more or less no matter where the screw is turned. The doughnut will still be seized in whatever position it's stuck no matter where the screw head turns.

A very close look with bright light will reveal if the doughnut is turning along with the screw head.

Or not.

This theory assumes that every one of these trimmer caps has been "snapped" except CT2.

Could be.

Does it change channels normally and appear to be locked onto the selected channel?

You didn't say.

73
 
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nomadradio said:
Makes me wonder if this radio was built with the white ceramic-body trimmer caps for CT4-6. You didn't mention CT3, so I'll guess that one behaves properly when you twist it.

That particular style trimmer cap can become seized. The metal-coated ceramic doughnut is what actually turns with the adjusting screw. The metalized layer on half of that doughnut is soldered to that screw.

If the doughnut gets stuck to the trimmer's body, the natural reaction is to twist harder.

Until a tiny "CRACK!" sound is heard and the screw suddenly turns freely.

Very freely. Because the solder connection from that screw to the metal coating on the doughnut is now broken. The trimmer will now be functionally stuck at minimum, more or less no matter where the screw is turned. The doughnut will still be seized in whatever position it's stuck no matter where the screw head turns.

A very close look with bright light will reveal if the doughnut is turning along with the screw head.

Or not.

This theory assumes that every one of these trimmer caps has been "snapped" except CT2.

Could be.

Does it change channels normally and appear to be locked onto the selected channel?

You didn't say.

73
Click to expand...
I wrote this using my phone and have since read it and corrected it. CT2 does not do anything either. I will take a look if these are spinning but seized. It just seems weird that it shows 22.XXX MHz no matter where the channel is set. I also tried to look for problems on that circuit board tape that runs from the PLL to the channel encoder. I have had problems there with other radios but that looks fine. Also The PLL on that schematic is shown in 3 or 4 different parts so it must be doing a lot.
 
Makes me wonder if L24 hasn't been twirled. When a PLL won't lock, the usual cause is a missing input signal to the PLL chip. Not always, just usually.

L24 tunes the third harmonic of the three 11 MHz crystals. I don't think L24 has the adjustment range to reach down to 22 MHz. But that would be the crystal's second harmonic.

Sure sounds like 'scope time. I'm not convinced you'll get this sorted out with a meter alone.

73
 
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My next step is pull all the Crystal's and check each one. What I do not understand is why nothing changes when the channel is changed. I can go from ch 1 to ch 40 but my frequency counter stays at 22.500 mkz. And does not change when the trimmer in the radio is adjusted
 

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